Retrieval methods for limb-scanning measurements usually adopt the assumption of horizontal homogeneity for the parcel of atmosphere sounded by the analyzed observations. For along-track observations from an orbiting platform, the dimension of the probed parcel of atmosphere may approach 2000 km. Horizontal homogeneity assumption in the inversion algorithms induces an error on the retrieved atmospheric parameters. Two questions arise from these considerations: 1) how to characterize these errors, 2) how to avoid this assumption if the size of the induced errors is not acceptable. In order to answer these questions, an innovative forward and retrieval model (geo-fit) was developed which does not use horizontal homogeneity assumption. In this approach the radiative transfer is made through a two-dimensional inhomogeneous atmospheric field. The retrieval algorithm is based on the simultaneous analysis of all the limb-scanning measurements relating to a given orbit. This feature allows to gather information from several contiguous limb-scanning sequences on a target atmospheric parameter at a given location, and therefore to improve the trade-off between accuracy and horizontal resolution. The obtained results show that the horizontal homogeneity assumption induces a significant systematic error on the retrieved atmospheric parameters, especially in the presence of strong horizontal gradients.